I am putting a new Piston and rings on my 1980 DT175G US model. I want to put a Wiseco piston in part number 471MO6650 or 471MO6700 depending on what the machine shop says on my bore.

Wiseco website says it will NOT fit 1980 only 1978 and 1979. Other sites says it will fit 1980. It has now the Wiseco.

Does anyone know if the 1980 is different from 1978 and 1979.


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I believe. But am not 100% sure that yamaha changed the piston and cyl head on the 3J1 model. The cylinder is the same as is the crank.
However piston and head have been revised.

This leads me to think that squish area dimensions were changed. I can see no reason otherwise for the part number change.

I've been guilty of really not paying any attention to any squish differences...  mostly because the gap is so large on the stock engine. 

I've used Wiseco, earlier pistons and rings in later models, and later rings and pistons in earlier models.  I've even trimmed the skirt on a Blaster piston a couple of times as they are readily available. 

I've never had an issue...  but that doesn't mean what I've done is correct or "best practice". 

I'm sure I have both heads around here someplace...  someday I'll have to dig them out and compare. 

That would be interesting because genuine ART NOS 3J1 pistons are far more readily available at a reasonable price than the 2A7/2N5 pistons in the UK.

What would you guys recommend for a piston kit. On my 1980 DT175G US model. 1mm over bore so 67mm.

Some sites say it fits some don’t.

There is also a Vintco piston made in Germany. I believe Wossner makes them. Some sites say it fits some don’t.

I would like to get a Yamaha kit by can’t find them.

Thanks for your input.


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I bought a Piston for my sons '80 175 a couple of years back, the vendor listed 2 pistons for the '80 but were different part numbers. The one I selected and bought was wrong, the pin height was wrong and the piston either sat too high or low, I don't recall. Maybe that's the difference with Wiseco?